The proposed U19 ICIDR Program is focused on human infection and disease by Leptospira. Our overall approach is to use fundamental biological scientific methods combined with clinical/field studies in contrasting epidemiological contexts in Peru and Sri Lanka, to develop new, clinically actionable diagnostic tests. Taking into account the local, regional, and international diversity of Leptospira, the proposed research addresses a hitherto insurmountable gap in the field, that of obtaining diagnostic tests for leptospirosis that are inexpensive, sensitive and efficient, yet easily deployable and effective regardless of the underlying transmission dynamics. The improved accuracy and efficiency of these tests will enable timely administration of appropriate therapy, which is vital for improving clinical outcomes. The overall goal of this Program is to develop robust tools and approaches that will effectively quantify the Global Burden of Leptospirosis, addressing several key goals shared by the international leptospirosis research community as articulated by the World Health Organization's Leptospirosis Epidemiology Reference Group (LERG).1, 2 These approaches, which are applicable to all leptospirosis-endemic and epidemic-prone sites, are summarized as follows: 1. Carry out prospective, field-based clinical studies of suspected acute leptospirosis cases in known or suspected highly endemic settings in Peru (Project 1) and Sri Lanka (Project 2) where the diversity of Leptospira is high and includes the most highly pathogenic as well as less pathogenic (but still infectious) Leptospira. These sites will include contrasting urban vs. rural and seasonal vs. perennial leptospirosis risk areas in Peru and Sri Lanka. The projects will focus on both hospitalized cases (more severe disease) and outpatients (generally mild spectrum of disease) with dedicated attention to comprehensively follow up clinical and microbiological/molecular outcomes; 2. Characterize serum and urine samples from field studies with regard to leptospirosis diagnosis using conventional serology (MAT, ELISA),3, 4, 5 routine culture, our published culture-independent molecular techniques (conventional PCR,6, 7 qPCR,8 Multi Locus Sequence Typing (MLST)9, 10); 3. Test newly developed antigen-detection tests (LPS; alternatively, Leptospira proteins) and antibody- based serological tests using protein microarray technology based on our newly developed Leptospira Genome Project database (PATRIC, http://patricbrc.org; deposited in GenBank, http://www.ncbi.nlm.nih.gov/bioproject/?term=leptospira (both accessed March 7, 2014)) against conventional diagnostics (gold standard re-defined as MAT (on paired samples) plus PCR of blood/urine, given the insensitivity of current culture techniques (problems with past gold-standard diagnostics discussed in Refs.11, 12). The expected outcomes of this program are 1) New tools to diagnose leptospirosis and to identify leptospiral infection of humans; 2) Define and optimize the generalizability of these new tools in diverse and representative settings in Peru and Sri Lanka, and beyond (for example, through the U.S. Centers for Disease Control and Prevention that receives samples from all over the world; see Renee Galloway, Letter of Support); and 3) Enhancing research capacity of foreign collaborators by facilitating development of independent creative scientific thinking, hypothesis generation and testing, and new approaches to addressing clinical and translational research problems of highest priority to the endemic country. Additional benefits from this project include clear application to OneHealth medicine because human leptospirosis reflects interactions of humans with zoonotic domestic and agricultural sources such as dogs, cattle, pigs, and water buffalo, wild and peridomestic rodents and marsupials. The tools developed here will have direct application and translation to veterinary and agricultural settings but such work will be beyond the scope of the present project.